Gels of carboxyalkyl ethers of carbohydrate gums



with a cold solution of alkali serves to disperse v Patented June 10,1952 GELS OF OARBOXYALKYL ETHERS F CARBOHYDRATE GUMS- Owen A. Moe,Minneapolis, Minn, assignor to General Mills, Inc., a corporation ofDelaware No Drawing. Application July 19, 1950, Serial N0. 174,785

13 Claims. (01. 260-209) 1 2 The present invention relates to gels ofthe gum without the occurrence of lumping. It is carboxyalkyl ethers ofcarbohydrate gums and also possible to disperse the gum in aqueous tomethods of producing the same. This applialkali at a more elevatedtemperature by a more cation is a continuation-in-part of my copendingefiicient stirring means. After dispersion of the application Serial No.664,987, filed April 25, 1946, 5 gum in aqueous alkali, the mixture isheated now Patent No. 2,510,161 which in turnis a conto an elevatedtemperature such as 60-90 C. and tinuation-impart of my applicationSerial No. the reaction mixture will then frequently become 612,717,filed August 25, 1945, now Patent No. semi-solid. This mass is thencooled and broken 2,477,544. up into fine particles and treated with theIn the above mentioned applications there are etherifying agent. Thisreaction mixture is then disclosed novel carboxyalkyl ethers ofcarbohyheated to a temperature of 8085 C. for an apdrate gums and alkalimetal salts thereof which preciable period Of time, 1 to 2 hours, withoff:- are readily dispersible and form sols of excellent cient mixing.The reaction mixture is then clarity. The present application isconcerned cooled and diluted with water and made acid with gels formedfrom sols of these carboxyalkyl to phenolphthalein. The reaction productmay others. then be precipitated by the addition of a water Theinvention is applicable to carbohydrate miscible organic solvent such asmethanol, acegums selected from the group consisting of gatone, and thelike, and may be washed with a lactomannan and gluoomannan gums. Thesesimilar mixture of water and organic solvent gums are polysaccharidescomposed principally for further removal of impurities, and then driedand ground.

Another method of making the carboxyethyl and substituted carboxyethylderivatives of the galactomannan and glucomannan type gums is asfollows: The gums are dispersed in an alkaline solution and then reactedwith acrylonitrile or substituted acrylonitriles such asmethacrylonitrile. This reaction results in a cyanoethyl ether of thegum which can then be'hydrolyzed in any suitable manner to produce thecarboxyethyl gum ether or the alkali metal salts thereof.

In forming the gels the carboxyalkyl ether of the gum is dispersed inwater to produce a sol.

Low concentration sols of from about 1% to 3% d of the carboxyalkylether are preferred. To these sols there is added an aqueous solution ofa polyvalent metal salt and the resultant mixture is stirred to producea gel. Wide variation is possible both in concentrations of the sols andthe salt solution and also in the relative ratios of these reactants. Itis also possible to vary the nature of the gel from a soft gel to a veryfirm gel by varying the quantities and the concentrations of thereactants. By routine examination it is possible to determinetheconcentrations and proportions of reactants for the production of anydesired type of gel with any particular sol.

of Jgalactose and mannose units and glucose and mannose unitsrespectively. The galactomannans are usually found in the endosperm ofleguminous seeds such as guar, locust bean, honey locust, flame tree,Cassia occidentalz's, and the like. The glucomannans on the other hand,are usually found in the corms of plants of the Araceae family such asAmorphophallus oncopfzyllus, from which the product known as iles mannanis obtained, and Amorphophallus rieieri from which knonnyaku flour isobtained.

Aqueous sols of the carboxyalkyl ethers of these gums are capable offorming gels on the addition of an aqueous solution of salts ofpolyvalent metals such as ferrous sulfate, aluminum sulfate, aluminumchloride, and the like. These gels are very firm and can be transferredfrom one container to another without wetting the surface withwhich theycome in contact.

It is therefore a primary object of the present 40 invention to providegels of carboxyalkyl ethers of carbohydrate gums selected from the groupconsisting of *gal'actomannan and glucomannan gums.

It is a further object of the present invention to provide a process ofproducing such gels.

The carboxyalkyl ethers may be formed by treating the gum with a coldaqueous solution of an alkali such as sodium hydroxide, and thentreating the alkali gum'with a halo fatty acid or a halo fatty acid saltsuch as sodium chloroacetate, sodium chloropropionate, sodiumchlorobutyrate, and other halo fatty acids or salts thereof. In general,the treatment of the gum Example 1 1.2 gramsof sodium carboxyethyl etherof guar gum were dissolved in grams of water'to yield a clear solution.The pH of the solution was adjusted to 6.6 with acetic acid. Theresultant solution was then divided into three equal portions. To oneportion was added an aquo m solution of ferrous sulfate and the mixturewas stirred, whereupon a gel resulted.

To a second portion was added an aqueous solution of aluminum sulfateand a gel resulted upon stirring.

To a third portion was added an aqueous solution of aluminum chlorideand a gel resulted upon stirring.

Example 2 To a series of 25 g. samples of a 2% sodium carboxymethyl guargum solution were slowly added varying quantities of aqueous ferroussulfate solution with complete stirring. Desirable gel formationoccurred in the samples to which from 5 to cc. of ferrous sulfatesolution had been added with the best type gel being obtained at from 8to 10 cc.

Similar results were obtained when a ferrous sulfate solution was addedall at once with efiicient stirring to the point where gelationoccurred.

Example 3 To four 10 gram samples of 3% aqueous sodium carboxymethylguar gum were added various amounts of 10% ferrous sulfate, stirringbeing applied only until the materials were thoroughly mixed andgelation occurred. It was found that best results were obtained by theuse of from 3 to 5 cc. of ferrous sulfate, and that gels could beobtained up to 12 00., but these were not as desirable as those producedwith lower quantities of ferrous sulfate.

Example 4 To 10 gram samples of 3% aqueous solution of sodiumcarboxymethyl guar gum were added varying quantities of aqueous ferroussulfate solution. It was found that exceptionally good gels wereobtained with from 1 to 2% cc. of the ferrous sulfate solution, and avery good gel was obtained at 4 cc. of ferrous sulfate solution, andthat acceptable gels were still formed at 6 cc. of ferrous sulfatesolution. Furthermore it was noted that these gels were firmer than thegels of Example 3, possibly due to the fact that in Example 3 gels weremore dilute.

Example 5 A 3% aqueous solution of sodium carboxy- Example 6 Forty partsof locust bean gum were dispersed in 150 parts of 7% sodium hydroxidesolution cooled to 0 C. The alkali-gum mixture was heated in a waterbath to 80 C. and the reaction mixture became semi-solid. The resultingmass was firm and rubbery-like. After cooling, this mass was broken upinto fine particles and the solution of the sodium chloracetate (23.5parts of chloracetic acid in parts of water was neutralized with 10parts of sodium hydroxide in 20 parts of water) was added with efiicientmixing. The resulting reaction mixture was heated in a water bath to80-85 C. for a period of 90 minutes with efficient mixing. Aftercooling, the reaction mixture was diluted with 200 cc. of water and madeacidic to phenolphthalein by addition of dilute acetic acid. Thereaction product was precipitated by the addition of methanol. The

precipitated product thus obtained was washed with methanol, dried andground to a powder. The sodium carboxymethyl ether of locust bean gumthus prepared was readily dispersible in water to form 1% sols ofremarkable clarity and stability and of a viscosity comparable to orhigher than that of the gum itself. A 3% sol of very good clarity andhigh viscosity was very readily obtained. These sols formed gels whichwere firm when a solution of a metallic salt such as ferrous sulfate wasadded. The gels may be prepared in the following manner: Three to fiveparts of a 10% ferrous sulfate solution are added to 10 parts of a 3%carboxymethyl gum ether sol with efficient mixing. The gel formationtakes place rapidly as the sol is stirred. It is, of course, apparentthat the concentration of the ferrous sulfate and gum derivative solsmay be varied over a wide range.

Example 7 Twenty parts of iles mannan fiour were easily disperseduniformly in 60 parts of 33% sodium hydroxide solution cooled to 0 C.This alkaligum mixture was heated in a water bath and a solid,rubber-like mixture resulted. This solid, rigid, yet rubber-like masswas cooled and ground into fine particles. Then 22 parts of chloraceticacid were mixed in well with cooling. After the addition of theetherifying agent was completed, the resulting reaction mixture washeated in a water bath to C. and maintained at this temperature for aperiod of minutes. The mixture was made acidic to phenolphthalein,cooled and diluted with 300 parts of water. The reaction mixture had adark color which was removed by precipitating the reaction product withmethanol. The precipitated product was treated in a usual manner. Thissodium carboxymethyl gum ether was readily dispersible in cold water toyield viscous 24% sols of good clarity and stability. This product alsoshowed the gel formation on the addition of a dilute ferrous sulfatesolution. However, the tendency towards this gel formation was not aspronounced as in the case of the derivative from locust bean gum andguar gum.

While these specific examples have been with particular reference tovarious salts of iron and aluminum, other polyvalent metal salts may beused for the production of gels. Different concentrations of thecarboxyalkyl ether derivatives and the salt solutions, as well as thequantities thereof, may be preferred, and the optimum conditions canreadily be determined by simple investigation.

I claim as my invention:

1. A gel comprising the reaction product of an aqueous sol of acarboxyalkyl ether of a gum selected from the group consisting ofgalactomannan and glucomannan gums, and a soluble polyvalent metal saltselected from the group consisting of iron and aluminum salts.

2. A gel comprising the reaction product of an aqueous sol of acarboxyalkyl ether of a gum selected from the group consisting ofgalactomannan and glucomannan gums, and a soluble aluminum salt.

3. A gel comprising the reaction prodct of an aqueous sol of acarboxyalkyl ether of a gum selected from the group consisting ofgalactomannan and glucomannan gums, and a soluble iron salt.

4. A gel comprising the reaction product of an an aqueous sol of acarboxyalkyl ether of a gum selected from the group consisting ofgalactomannan and gulcomannan gums, and aluminum sulfate.

5. A gel comprising the reaction product of an aqueous sol of acarboxyalkyl ether of a gum selected from the group consisting ofgalactomannan and glucomannan gums, and ferrous sulfate.

6. A'gel comprising the reaction product; of an aqueous sol of acarboxymethyl ether of a galactomannan gum and ferrous sulfate.

7. A gel comprising the reaction product of an aqueous sol of acarboxyethyl ether of a galacto-' mannan gum and ferrous sulfate.

8. A gel comprising the reaction product of an aqueous sol of aearboxymethyl ether of a galactomannan gum and aluminum sulfate.

9. A gel comprising the reaction product of an aqueous sol of acarboxyethyl ether of a galacticmannan gum and aluminum sulfate.

10. Process of producing a gel comprising preparing an aqueous sol of acarboxyalkyl ether of a gum selected from the group consisting ofgalactomannan and glucomannan gums, and adding thereto an aqueoussolution of a soluble polyvalent metal salt selected from the groupconsisting of iron and aluminum salts.

11. Process of producing a gel comprising preparing an aqueous sol of acarboxyalkyl ether of a gum selected from the group consisting ofgalactomannan and glucomannan gums, and

6 adding thereto an aqueous solution of aluminum sulfate.

12. Process of producing a gel comprising preparing an aqueous sol of acarboxyalkyl ether of a gum selected from the group consisting ofgalactomannan and glucomannan gums, and adding thereto an aqueoussolution of ferrous sulfate.

13. Process of producing a' gel comprising preparing an aqueous sol of acarboxyalkyl ether of a gum selected from the group consisting ofgalactomannan and glucomannan gums, and mixing said s01 with apolyvalent metal salt selected from the group consisting of iron andaluminum salts.

OWEN A. MOE.

REFERENCES CITED The following references are 01' record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,144,522 Braun Jan. 17, 19392,520,161 Moe Aug. 29, 1950 OTHER REFERENCES Mantell, Water SolubleGums, 1947, pages 234- 235 citing Jacobs et al., Ind. Eng. Chem. Anal.Ed. 3, 210-12 (1931).

Chem. Abst., vol. 43 (1949), p. 8717.

1. A GEL COMPRISING THE REACTION PRODUCT OF AN AQUEOUS SOL OF ACARBOXYALKYL ETHER OF A GUM SELECTED FROM THE GROUP CONSISTING OFGALACTOMANNAN AND GLUCOMANNAN GUMS, AND SOLUBLE POLYVALENT METAL SALTSELECTED FROM THE GROUP CONSISTING OF IRON AND ALUMINUM SALTS.